1. Field of the Invention
The present invention broadly relates to grain or seed drills and, more particularly, to grain drills which are provided with pneumatic means to meter and propel the seeds to open ground furrows.
2. Description of the Prior Art
Due to the hunger of the increasing world's population there is a corresponding increasing demand for more food output per acre. A way of meeting this increased demand is by increasing the efficiency of the farmer. One specific way of increasing the farmer's efficiency is by improved seed planting devices. Numerous generations of mechanized seed planting devices have been developed with each being an advance over the preceeding generation. Currently the majority of planting or seeding is carried out by devices called grain drills which consist of seed boxes attached to a rear portion of plows or furrow openers and deposit seeds at preselected intervals into furrows. These prior art grain drills may also be attached to separate wheeled trailers, but this is generally cost prohibitive.
Due to the extreme localized weight of the seed and the weight of the grain drill on the rear portion of the grain drill plows these prior art grain drills are only manufactured in relatively small units so to be easily carried. The small size of the seed boxes necessitates frequent refilling. Also the greater number of grain drills increases the cost of initial purchase and repair to the farmer. Several small grain drills can be pulled in squandron hitches, but this is cumbersome to operate.
Air powered grain drills have been designed in the past, however each has disadvantages, such as small size, irratic seed delivery and lack of means to selectively block the delivery tubes for specific seeding pattern, for different grains or other seed-like material. Some drills use venturi principles which are open to pick up dirt, dust particles and debris which commonly exist when drilling seed and which have been known to plug such delivery tubes causing underseeding and overseeding.